Having discovered a new mechanism of CO reaction and a new method of getting CO off rates, we will determine CO on and off rates for our models in a number of solvents and for several structures which we have in hand in order to complete our study of structure and solvent vs. CO and O2 reactivity in these models. We will use the accurate off-rate method mentioned above to determine all four CO rate constants in the diheme compound (II) and study the details of its heme-heme interaction. We plan to search for base elimination mechanisms in hemoproteins using flow and flow-flash methods to generate the deoxy species (B-Hm). Using laser photolysis and very fast (10 to the minus 6th power sec) detection we will search for the rate k which leads to an equilibrium K equals k'/k. This equilibrium is usually not seen, being perhaps 10 to 100 in, e.g., myoglobin, but it should be detectable by kinetic techniques if it is K less than 50. We think it will be less than 50 in some cases, even at pH equals 7 and much less than 50 at lower pH. BIBLIOGRAPHIC REFERENCES: Dual Pathways of Heme Protein Model Compound Reactions with Carbon Monoxide. J. Cannon, J. Geibel, M. Whipple, and T. G. Traylor, J. Amer. Chem. Soc., 98, 3395 (1976).